The DC system is an important part of electrical power installations, any earth faults can affect the operation of vital components, such as the system protection, circuit breakers and communication equipment. Therefore, its correct operation is vital to the stability of the network.

As the DC system is a floating unearthed system, an earth fault on one terminal will not prevent the system from working normally. However, should an earth fault occur simultaneously on the other terminal, it will result in a virtual short-circuit between them through the earth, causing the failure of the DC supply.

The ZDT-300 DC Earth Fault Locator is used to quickly and accurately locate DC network earth faults on live systems. It consists of a signal transmitter, receiver and a choice of sensors for different cable sizes. Depending on the model chosen, the system is capable of detecting high resistance faults up to 1MΩ, allowing problems to be identified at an early stage, so that remedial action can be taken to prevent a subsequent failure.